scholarly journals Changes of of extracellular potassium concentration induced by neuronal activity in the spinal cord of the cat

1974 ◽  
Vol 238 (1) ◽  
pp. 1-15 ◽  
Author(s):  
N. Kříž ◽  
Eva Syková ◽  
E. Ujec ◽  
L. Vyklický
Keyword(s):  
Spinal Cord ◽  
Neuronal Activity ◽  
Potassium Concentration ◽  
Extracellular Potassium ◽  
Extracellular Potassium Concentration

Increasing Extracellular Potassium Results in Subthalamic Neuron Activity Resembling That Seen in a 6-Hydroxydopamine Lesion

2008 ◽  
Vol 99 (6) ◽  
pp. 2902-2915 ◽  
Author(s):  
Ulf Strauss ◽  
Fu-Wen Zhou ◽  
Jeannette Henning ◽  
Arne Battefeld ◽  
Andreas Wree ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Potassium Concentration ◽  
Neuron Activity ◽  
Extracellular Potassium ◽  
Action Potential Firing ◽  
Extracellular Potassium Concentration ◽  
Potential Firing ◽  
6 Hydroxydopamine

Abnormal neuronal activity in the subthalamic nucleus (STN) plays a crucial role in the pathophysiology of Parkinson's disease (PD). Although altered extracellular potassium concentration ([K+]o) and sensitivity to [K+]o modulates neuronal activity, little is known about the potassium balance in the healthy and diseased STN. In vivo measurements of [K+]o using ion-selective electrodes demonstrated a twofold increase in the decay time constant of lesion-induced [K+]o transients in the STN of adult Wistar rats with a unilateral 6-hydroxydopamine (6-OHDA) median forebrain bundle lesion, employed as a model of PD, compared with nonlesioned rats. Various [K+]o concentrations (1.5–12.5 mM) were applied to in vitro slice preparations of three experimental groups of STN slices from nonlesioned control rats, ipsilateral hemispheres, and contralateral hemispheres of lesioned rats. The majority of STN neurons of nonlesioned rats and in slices contralateral to the lesion fired spontaneously, predominantly in a regular pattern, whereas those in slices ipsilateral to the lesion fired more irregularly or even in bursts. Experimentally increased [K+]o led to an increase in the number of spontaneously firing neurons and action potential firing rates in all groups. This was accompanied by a decrease in the amplitude of post spike afterhyperpolarization (AHP) and the amplitude and duration of the posttrain AHP. Lesion effects in ipsilateral neurons at physiological [K+]o resembled the effects of elevated [K+]o in nonlesioned rats. Our data suggest that changed potassium sensitivity due to conductivity alterations and delayed clearance may be critical for shaping STN activity in parkinsonian states.

GABA-Receptor–Independent Dorsal Root Afferents Depolarization in the Neonatal Rat Spinal Cord

1998 ◽  
Vol 79 (5) ◽  
pp. 2581-2592 ◽  
Author(s):  
E. Kremer ◽  
A. Lev-Tov
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Gaba Receptor ◽  
Neonatal Rat ◽  
Extracellular Potassium ◽  
Rat Spinal Cord ◽  
Extracellular Potassium Concentration ◽  
Dorsal Roots ◽  
Intact Brain ◽  
Dorsal Root Afferents

Kremer, E. and A. Lev-Tov. GABA-receptor–independent dorsal root afferents depolarization in the neonatal rat spinal cord. J. Neurophysiol. 79: 2581–2592, 1998. Dorsal root afferent depolarization and antidromic firing were studied in isolated spinal cords of neonatal rats. Spontaneous firing accompanied by occasional bursts could be recorded from most dorsal roots in the majority of the cords. The afferent bursts were enhanced after elevation of the extracellular potassium concentration ([K+]e) by 1–2 mM. More substantial afferent bursts were produced when the cords were isolated with intact brain stems. Rhythmic afferent bursts could be recorded from dorsal roots in some of the cords during motor rhythm induced by bath-applied serotonin and N-methyl-d-aspartate (NMDA). Bilaterally synchronous afferent bursts were produced in pairs of dorsal roots after replacing the NaCl in the perfusate with sodium-2-hydroxyethansulfonate or after application of the γ-aminobutyric acid-A (GABAA) receptor antagonist bicuculline with or without serotonin (5-HT) and NMDA. Antidromic afferent bursts also could be elicited under these conditions by stimulation of adjacent dorsal roots, ventrolateral funiculus axons, or ventral white commissural (VWC) fibers. The antidromic bursts were superimposed on prolonged dorsal root potentials (DRPs) and accompanied by a prolonged increase in intraspinal afferent excitability. Surgical manipulations of the cord revealed that afferent firing in the presence of bicuculline persisted in the hemicords after hemisection and still was observed after removal of their ventral horns. Cutting the VWC throughout its length did not perturb the bilateral synchronicity of the discharge. These findings suggest that the activity of dorsal horn neurons is sufficient to produce the discharge and that the bilateral synchronicity can be maintained by cross connectivity that is relayed from side to side dorsal to the VWC. Antagonists of GABAB, 5-HT2/5-HT1C, or glutamate metabotropic group II and III receptors could not abolish afferent depolarization in the presence of bicuculline. Depolarization comparable in amplitude to DRPs, could be produced in tetrodotoxin-treated cords by elevation of [K+]e to the levels reported to develop in the neonatal rat spinal cord in response to dorsal root stimulation. A mechanism involving potassium transients produced by neuronal activity therefore is suggested to be the major cause of the GABA-independent afferent depolarization reported in our study. Possible implications of potassium transients in the developing and the adult mammalian spinal cord are discussed.

Disorders of potassium homeostasis

2010 ◽  
pp. 3831-3845 ◽  
Author(s):  
J Firth
Keyword(s):  
Membrane Potential ◽  
Potassium Concentration ◽  
Resting Membrane Potential ◽  
Extracellular Potassium ◽  
Normal Range ◽  
Critical Determinant ◽  
Potassium Homeostasis ◽  
Extracellular Potassium Concentration

The normal range of potassium concentration in serum is 3.5 to 5.0 mmol/litre and within cells it is 150 to 160 mmol/litre, the ratio of intracellular to extracellular potassium concentration being a critical determinant of cellular resting membrane potential and thereby of the function of excitable tissues....

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